diff --git a/browser/css/notebookbar.css b/browser/css/notebookbar.css
index 468cfc34ea51..f92c8bf79141 100644
--- a/browser/css/notebookbar.css
+++ b/browser/css/notebookbar.css
@@ -394,6 +394,7 @@ html[data-theme='dark'] .savemodified.unotoolbutton .unobutton img {
 	scrollbar-width: none;
 	background-color: var(--color-stylesview-background);
 	filter: brightness(var(--brightness-stylesview));
+	box-sizing: border-box;
 }
 
 #stylesview:hover {